At some point in the next month, a working group will be formed to ponder the proper ratio of sunlight to shade in San Francisco's public parks - the urban design equivalent of trying to count the number of angels on the head of a pin.

The real question is whether such a task force can move beyond preordained positions and explore something more radical: an approach to urban design that embraces the complexity of the times in which we live.

That's a tall order for a working group conceived in response to single-issue politics of the most simplistic sort.

I'm referring to the short-lived Park Sunlight Protection Ordinance that Supervisor David Chiu prepared for the June ballot. It tightened shadow restrictions already in place for downtown parks by taking away the discretion of city commissions to allow buildings that might cast a bit of extra shadow but provide other benefits. It also extended protection to plazas on Market Street and all open space within the three blocks of Yerba Buena Gardens.

The proposal surfaced in late January when Chiu and four fellow supervisors moved to place it on the ballot without running the details by planners or the public. Two weeks of saber-rattling later it sank; Chiu and Mayor Gavin Newsom agreed instead to assemble a task force to discuss how the 1980s-era protections might be strengthened or tweaked.

Task force has chance

Now, aides to the two politicians are working with the San Francisco Planning + Urban Research Association (SPUR) to craft a list of participants that all sides can agree on. There's a desire to move quickly, so that the task force can wrap up work by early summer.

This would leave time, if desired, for a ballot measure in November to endorse the findings - or, if opponents of tall buildings feel boxed in, an initiative along the lines of what Chiu proposed.

Task forces often are the last thing needed in a city as politically devious as San Francisco; they're an invitation to endless process, or a way for insiders to twist the rules to their advantage. This one, though, has a chance to succeed.

The reason, oddly, is that any discussion about preserving the ambiance of public parks will likely move away from the absolutist position of the proposed ballot measure - which, in essence, was that the protection of sunlight is more important than any other issue that might shape how San Francisco grows and evolves.

An example? No sane person would say that shadows are the most dire threat to perennially troubled United Nations Plaza. But if keeping the current amount of sunlight trumps all else, then you couldn't add anything nearby that, in return for minor slivers of occasional shade, might bring needed year-round vitality to that stretch of Market Street.

'Stealth weapon'

At its most cynical level, a sanctimonious push for "park sunlight protection" is a stealth weapon aimed at buildings or plans that already have gone through extensive public review. It taps into a visceral dislike of the tall or the new: the recent towers I hear the most complaints about, One Rincon and the San Francisco Federal Building, are lightning rods for their visual prominence rather than the shadows they cast.

But it's also absurd to insist that towers must sprout everywhere like mushrooms to create jobs or produce large amounts of housing. Emphasizing quantity rather than quality would erode the city's long-term health.

If the working group mission is framed as an affirmative - how do we nurture parks and plazas as enticing environments - then it can provoke a discussion that's long overdue.

The fact is, there are good reasons for San Francisco to grow. They range from the quest for regional sustainability to the vibrancy of districts like Yerba Buena that concentrate culture and life in tall buildings around well-maintained plazas and parks.

Downtown open spaces aren't just sylvan retreats. Their urban setting can help make them thrive.